For some unknown reason, at least for me (license most likely) there is no Scratch package in Debian as long I remember the problem could be that the name and the mascot are trademarks (same problem that with Firefox / Iceweasel), any case there is a .deb package for Ubuntu, that of course tested on my Debian 6 (current stable) and hit with the problem that a lot of people had found, there is no easy way to install it on Debian because of broken dependencies, specially that the Ubuntu version requires pulseaudio => 1.0.9 and in Debian we had pulseaudio 0.9.21-3+squeeze1, on Wheezy is used 1.0-4, but reading on the net there are really ugly hacks to install this package forcing deps, hacking dpkg controls and so on, but the interesting thing was that even with the oldest version of pulseaudio this package works! So why no hack the package instead of hack my installation?
Now knowing that the dependencies control is on a file called control, I found without too much search a nice recipe in the Ubuntu forums  really searching for other thing
In my case I create a directory called 1 (you can use test, temp, etc.)
Extract the contents of the Deb.
dpkg-deb -x scratch_184.108.40.206-0ubuntu5_i386.deb 1/
dpkg-deb –control scratch_220.127.116.11-0ubuntu5_i386.deb 1/
edit the contents of 1/DEBIAN/control
vi 1/DEBIAN/contro (change vi for nano, emacs or whatever you use to edit text)
now change the pulseaudio =>1.0.9 for =>0.9.2 (you can be safe using 0.9 instead), save and exit.
We need to rebuild our package
dpkg -b 1/ scratch_18.104.22.168-0ubuntu5_i386.modified.deb
And that’s it our package now can be installed on Squeeze or Wheezy without problems or at least without breaking the dpkg control, colliding with next updates and more or less work along with the system. I listed all the steps but again in the Ubuntuforums I found that someone found this so easy (or uneasy) that wrote a script  and to make it better it’s on githhub  to anyone to fork and contribute, and of course maybe you now where wondering where I download Scratch? Well from their MIT site , after done this I was thinking on report this as an issue on their trac, just to find that there is already reported!  in case you find this instructions too hard I have upload the package on my previous post  or directly you can grab here